Two stage forming with expanding skirt step



Nov. 15, 1966 J. w. BERG 3,235,045

TWO STAGE FORMING WITH EXPANDING SKIRT STEP Filed April 13, 1964 Fig.1

20 Fig.2

Fig. 4 F 5 INVENTOR.

JOHN W. BERG United fitates Patent 3,285,045 TWO STAGE FORMING WITHEXPANDING SKIRT STEP John W. Berg, La Mesa, Calif., assignor, by mesneassignments, to The Bendix Corporation, a corporation of Delaware FiledApr. 13, 1964, Ser. No. 359,299 3 Claims. (Cl. 72-54) This inventionrelates generally to -a method of expanding metal by the use ofhydraulic pressure and more particularly to a two stage forming processin which a clamping ring having an enlarged internal diameter is used toclamp the material during the second expanding step.

BACKGROUND In the past, it has been common practice to produce deepdraws in sheet material by gripping the edge of a blank and eitherstriking it by mechanically operated dies or subjecting it to fluidpressure. These methods resulted in uneven work hardening of the sheetmaterial and to overcome this it was necessary to stretch the materialin several stages, removing the material and heat treating it betweenoperations. This produced a fairly uniform hardness in the finishedarticle but added greatly to the expense of producing it.

According to the present invention very deep draws can be made, with auniform degree of hardness, by utilizing a two step process in which anenlarged diameter clamping ring is used during the second stage of theprocess.

OBJECTS AND DRAWINGS It is the primary object of this invention toprovide an improved method of deep drawing sheet material by which thefinal properties of the finished article may be accurately controlled.

It is a further object of this invention to provide an improved methodof deep drawing sheet material which will produce a finished articlehaving uniform hardness throughout.

It is a still further object of this invention to provide an improvedtwo stage method of facilitating deep draws in sheet material.

With these and other objects definitely in view, this invention consistsin the novel construction, combination and arrangement of elements andportions, as will be hereinafter fully described in the specification,particularly pointed out in the claims, and illustrated in the drawingwhich forms a material part of this disclosure, and in which:

FIGURE 1 is a cross section of a sheet material blank prior to theinitial working step;

FIGURE 2 shows a cross section of a suitable fluid pressure drawingapparatus with a sheet material blank therein as it appears at the endof the first stage of the process;

FIGURE 3 is a similar cross section of the apparatus used for the secondstage of the process with the blank expanded to finish form;

FIGURE 4 shows the blank on a reduced scale as it appears when removedfrom the apparatus shown in FIG- URE l; and

FIGURE 5 shows the finished article with a portion of the skirt ofFIGURE 3 expanded.

With particular reference to the drawing I have shown, in FIGURE 1, apiece of stock sheet material of any desired thickness. I prefer to usemetal but it is within the scope of this disclosure to use any of thewell known synthetic plastics such as nylon or Dacron. The blank 10 isshown as being circular in shape but the process is of blank 22.

3,Z85,fi Patented Nov. 15, 1966 ice In FIGURE 2 I have illustrated thebasic elements of the apparatus used in the first stage of the process.A base plate 12, suitably mounted on any convenient supportingstructure, is provided with a plurality of mounting studs 14 spacedaround the periphery thereof. A clamping ring 16 is secured on the studsby the usual nuts 18. This clamping ring is representative only it beingunderstood that other types of clamping means, well known in the art maybe substituted therefore. Base plate 12 is connected to a suitablesource of fluid under pressure by conduit 20.

With the base plate 12 suitably mounted on a supporting structure, theconduit 20 cut off from the pressure source by any suitable valve meansand the clamping ring 16 separated from the base plate, blank 10 isplaced on the upper surface of the base plate, properly centered andclamped by placing clamping ring 16 on studs 14 and tightening nuts 18to hold the periphery of the blank against slipping. Fluid pressure isthen admitted to conduit 2t and blank 10 is stretched to an intermediateshape such as 22. in FIGURES 2 and 4. It will be apparent that duringthis initial stretching stage the central bowed portion of the blank isstretched more than those portions of the blank at points 24, in FIGURE4, which are adjacent the bend. This uneven stretching produces a workhardening that is greatest at the central portion and gradually tapersofi toward the edges 24 of the worked portion of the intermediate blankshown in FIGURE 4.

Pressure is now reduced to approximately that of the ambient atmospherein conduit 21) and clamping ring 16 removed and replaced by clampingring 26 which is of larger internal diameter than ring 16 as clearlyshown in FIGURE 3. Ring 25 is tightened in place to grip and hold theskirt of blank 22 against slipping and fluid-pressure is again appliedthrough conduit 20 to the underside Blank 22 will be expanded andstretched to an increased diameter by this second stage of the drawingprocess. The skirt 28 of the intermediate blank will be reduced in widthas shown by 39 in the finished product of FIGURE 5. During this secondstage expansion the greatest proportion of stretching, and consequentlywork hardening, will take place in the area of point 24- which will havemoved to a position, as shown in FIG- shape of the finished product.

URE 5. This will produce, in the finished article, a substantiallyuniform hardness throughout the worked surface. As soon as the desiredfinished shape is reached pressure in conduit 20 is reduced and thefinished article is removed by releasing the clamping ring.

From the foregoing description it will be evident that the applicationof my improved two stage deep-drawing process will produce articleshaving uniform metallurgical characteristics. A deeper draw is possiblewithout the use of intermediate annealing steps thus greatly reducingthe cost of the finished article.

While I have shown the finished product as being substantiallyhemispherical, it is to be understood that hollow bodies of virtuallyany shape may be formed depending upon the initial shape of the blank10.

It is understood that minor variation from the form of the inventiondisclosed herein may be made without departure from the spirit and scopeof the invention, and that the specification and drawings are to beconsidered as merely illustrative rather than limiting.

I claim:

1. A method of forming deep-drawn sheet material parts from generallyflat sheet material blanks comprising the steps of:

clamping a peripheral area of said blank to prevent movement of saidperipheral area;

producing a drawing fluid pressure on one surface of said blank topartially extend the material and produce a central bowed portion insaid blank;

clamping a reduced peripheral area of said blank to prevent movement ofsaid reduced peripheral area and to expose an area of unworked material;and

producing a further drawing fluid pressure on said one surface to extendthe newly exposed area While said bulged portion is free to move undersaid further drawing fluid pressure. 2. A method for forming deep-drawnsheet material parts from generally flat sheet material blankscomprising the steps of:

clamping a peripheral area of said blank on a given diameter to preventmovement of said peripheral area;

producing a drawing pressure by fluid on one surface of said blank topartially extend the material and produce a central bowed portion insaid blank;

clamping a reduced peripheral area of said blank to expose an area ofunworked material to prevent movement of said reduced peripheral area;and

producing a further drawing pressure by fluid on said one surface toenlarge the newly exposed area while said bowed portion is free to moveunder said further drawing pressure, whereby the hardness of saidfinished article will be substantially uniform. 3. A method for formingdeep-drawn sheet material parts from generally flat sheet materialblanks comprising the steps of:

clamping said blank around its edges to prevent movement of the same;producing a drawing pressure by fluid on one surface of said blank topartially extend the material and pro- 5 duce a central bowed portion insaid blank;

clamping a reduced peripheral area of said blank to prevent movement ofthe same and to expose an area of unworked material; and producing afurther drawing pressure by fluid on said one surface to extend thenewly exposed area While said bowed portion is free to move under saidfurther drawing pressure, whereby the hardness of said finished articlewill be substantially uniform.

References Cited by the Examiner UNITED STATES PATENTS 495,591 4/1893Knight et al. 72349 1,625,914 4/1927 Seibt 72-54 2,232,098 2/1941Deichman 113l20 FOREIGN PATENTS 785,453 5/1935 France.

CHARLES W. LANHAM, Primary Examiner. RICHARD J. HERBST, Examiner.

1. A METHOD OF FORMING DEEP-DRAWN SHEET MATERIAL PARTS FROM GENERALLYFLAT SHEET MATERIALS BLANKS COMPRISING THE STEPS OF: CLAMPING APERIPHERAL AREA OF SAID BLANK TO PREVENT MOVEMENT OF SAID PERIPHERALAREA; PRODUCING A DRAWING FLUID PRESSURE ON ONE SURFACE OF SAID BLANK TOPARTIALLY EXTEND THE MATERIAL AND PRODUCE A CENTRAL BOWED PORTION INSAID BLANK; CLAMPING A REDUCED PERIPHERAL AREA OF SAID BLANK TO PREVENTMOVEMENT OF SAID REDUCED PERIPHERAL AREA AND TO EXPOSE AN AREA OFUNWORKED MATERIAL; AND PRODUCING A FURTHER DRAWING FLUID PRESSURE ONSAID ONE SURFACE TO EXTEND THE NEWLY EXPOSED AREA WHILE SAID BULGEDPORTION IS FREE TO MOVE UNDER SAID FURTHER DRAWING FLUID PRESSURE.